GEOLOGY OF THE GREEN MOUNTAINS IN MASSACHUSETTS. 



GENERAL STRUCTURE AND CORRELATION 



By Raphael Pumpelly 



GENERAL DESCRIPTION. 



The Green mountains, nearly coinciding with the prolongation of the 

 axis of the Archean core of the Appalachians through western New Eng- 

 land, stand between the less disturbed fossiliferous Paleozoic strata of New 

 York and the highly crystalline rocks of New England. They consist of 

 three principal structural elements : The Green mountains (Hoosac moun- 

 tain) ; the Taconic range, lying several miles to the west; and, between 

 these, the great valley. But the whole region between the Hudson and the 

 Connecticut lias very properly been placed by Dana in one mountain sys- 

 tem. I shall therefore follow Dana and distinguish between a central or 

 axial ridge, flanked by an eastern belt extending to the Connecticut, and a 

 western belt extending to the Hudson, though what I shall have to say refers 

 mainly to the central belt and the neighboring portion of the western belt. 



The Green mountain range is composed of crystalline schists, which 

 our results show to be of Cambrian and Lower Silurian age, resting on pre- 

 Cambrian rocks, and it was long ago shown by Edward Hitchcock to have 

 an anticlinal structure. The western edge of this axial range is, for long 

 stretches, marked by a lofty brow of quartzite, and for this reason the 

 mountains present a very steep flank on the west. At the base of this 

 western flank lies what is known as the valley of Vermont or, in Massachu- 



